It is well known that the cost of auto repairs have been significantly increasing because of the complexity of automobiles, the cost of replacement parts and the time required to do the repairs. Moreover, automobiles are generally being used for longer periods and driven a greater number of miles before replacement than was heretofore the case, and increasing numbers of automobile owners are finding it useful, or even necessary, to do their own required repair work and routine maintenance. However, while a great deal of such work is within the capability of auto owners having limited skills, special tools are frequently required or would be helpful in avoiding problems that may arise due to lack of experience of the repairman.
For example, most automobiles are fitted with "disc" brakes on at least two of the wheels. Braking of the vehicle results from hydraulically driven caliper pistons being energized by the driver, which act on brake pads to engage a metal disc rotating with the wheels of the vehicle. Due to the severe service experienced by a vehicle's braking system, the attendant wearing of the brake pads require their periodic replacement to maintain the operability thereof and avoid damage to other parts of the brake system. As is known, most brake pads are replaceable, generally as a maintenance item. One conventional procedure that is widely used for that purpose involves the following general steps:
Drain some brake fluid from the master cylinder; the insertion of thicker replacement brake pads will push the caliper pistons back into their bores (hydraulically driven pressure device for applying brake pads against the revolving disc) and cause a full master cylinder to overflow;
raise and support the car and remove the wheels; extract and discard the cotter pin found on the inside end of the brake pad retaining pin(s); PA1 withdraw the retaining pin(s) and remove the worn pads; PA1 force the caliper pistons into their bores and insert the replacement pads; PA1 replace the retaining pins and secure them with new cotter pins; and PA1 refill the master cylinder and bleed the system, if necessary.
These basic steps appear quite simple and routine, and they should be. However, when working with vehicles having heavy-duty braking systems such as two spring-loaded caliper pistons, both pistons must be forced into their bores to remove the worn brake pad and replace it with a thick, new pad. The caliper piston springs are quite strong and the pistons, which are hydraulically operated, have rubber sealing parts which can be easily damaged.
Generally, in such multiple, spring-loaded piston systems, it is difficult, if not impossible, for one person to install new pads without damage to other parts and/or drawing air into the hydraulic braking system. Two or more separate pistons must be pushed back into their bores and then securely restrained within the bores while the old pad is being removed and a new pad is installed. The old brake pad may be used to push both piston springs back into the caliper bores, but it is necessary to remove the worn pad before a new one can be installed.
Control of the spring-loaded pistons during this phase of the operation is quite important since, for example, extension of the piston due to lack of adequate restraint, will cause air to be drawn into the system, usually past the rubber parts, and collects in areas which are difficult to bleed. Thus, supplemental means for restraint such as provided by another individual with a tool or clamp, are needed to safely install the new pads. An automobile repair shop generally can rely on the availability of several workers, but the automobile owner simply does not have the assistance available to perform what could be a routine maintenance operation.
In accordance with the foregoing, it may be regarded as an object of the present invention to provide a tool for readily replacing the brake pads in vehicle heavy-duty disc brake systems.
A further object of the invention is to provide a tool suitable for use by an individual in the ready replacement of brake pads in automobile multiple, spring-loaded piston disc brake systems.
A still further object of the invention is to provide a tool adapted for use with one hand in the maintenance of automobile disc brake systems having calipers with two spring-loaded pistons, whereby said tool retains both caliper springs while a worn disc brake pad is being removed and a new disc brake pad is being inserted in its place.